In active matrix drive display devices having, for example, liquid crystal display elements or organic electroluminescence (EL) elements as display elements, thin-film transistors (TFTs) are commonly used as driving elements for the display elements.
In display device products, TFTs in which a silicon layer is used as a semiconductor layer are commonly used. Now, however, more attention is being given to TFTs in which an organic material layer is used as a semiconductor layer. Unlike atomic bonding in silicon crystals for example, the binding forces acting in organic materials are intermolecular forces, and hence organic materials are flexible. Therefore, by using TFTs in which an organic material layer is used as a semiconductor layer, it is possible to realize lighter and thinner electronic devices compared to electronic devices using TFTs in which a silicon layer is used as a semiconductor layer, and it is also possible to provide flexibility to the electronic devices. For this reason, there is a proposal to use such TFTs, in which an organic material layer is used as a semiconductor layer, in next-generation display devices and electronic paper, for example. Regarding TFTs in which an organic material layer is used as a semiconductor layer, Patent Literature 1 discloses a coating-type TFT in which a semiconductor layer is formed by a coating method.
FIG. 28 is a schematic top view illustrating an example configuration of a common coating-type TFT 900.
As shown in FIG. 28, the TFT 900 includes a pair of a source electrode 904S and a drain electrode 904D, a bank 905, and a semiconductor layer 907. The bank 905 defines an aperture 906 where the semiconductor layer 907 is to be formed. The lateral surface of the bank 905 surrounding the aperture 906 is formed to be liquid-phobic. The semiconductor layer 907 is formed within aperture 906. The semiconductor layer 907 is formed in the following manner. First, semiconductor ink is prepared by dispersing organic material for forming the semiconductor layer 907 in a solvent. Next, the semiconductor ink is applied within the aperture 906. Finally, the solvent contained in the semiconductor ink is dried to evaporate. Thus, the semiconductor layer 907 is formed within the aperture 906.